The Lachmann method

It is widely accepted that stemmatics originated in the work of Karl Lachmman. However, other scholars have also argued that manuscripts can be shown to be related by copy. The idea goes as far back as Erasmus. We then should understand that Lachmann was the first to propose this method as a systematic approach which could help in the editing of texts. It would be incorrect, however, to assume that Lachmann wrote specifically about a particular methodology or theoretical approach. Instead, Lachmann's ideas can be found scattered in the introduction to his editions and in separate articles.
The formal formulation of the Lachmann method comes from Paul Maas' book and it presents his own interpretation of what Lachmann was trying to achieve. For those who have no access to the Lachmann editions —in German—, Maas is the most easily accessible source. This does not mean that Maas accurately represented Lachmann or that the method retains the essence of the German editions.
The Lachmann method, as formulated by Paul Maas, uses common errors in manuscripts to determine if they are or are not related and that assumes that the process of understanding the textual tradition must be carried out before one can decide which variants are to enter the emended text. These processes are known as recensio and emendatio.

Reactions against Lachmann method

Many scholars have reacted against the ideas in Paul Maas' book, and the Lachmann method has been attacked because of its seemingly scietific and heartless approach to texts. One of the strongest arguments against the method was advanced by Giorgio Pasquali, who especially disagreed with the supposition that every textual tradition must descend from a single archetype, and demonstrated the method's lack of utility, when strictly applied.

Modern genetic methods: the New Stemmatics

It is surprising to discover how many scholars use modern genetic methods —some of them which are closely related to Lachmann's ideas— despite the criticism that traditional genetic methods have endured through the years. It is possible to find a range of scholars using different variants of the Lachmann approach: including some who use what is known as Neo-Lachmannian approaches (Ben Salemans); some who have developed Lachmann's original ideas in order to take into account other aspects of the textual tradition (such as myself, Peter Robinson and our partners in the STEMMA and TEXTNET projects).
For some years now, we have been working on developing an approach that we refer to as the New Stemmatics. This method takes advantage of the almost limitless capacity of computers to handle and classify data and of the development and application of techniques such as phylogenetic analysis. The New Stemmatics takes into account all variant readings, not just errors, when analysing a textual tradition. It offers a different way to approach texts and complex traditions and it presents an alternative editorial method. When edited texts are not required, textual variations are presented in a way which makes it easier for the reader to understand the differences between the texts. If an edited text is needed and its production possible, then editors would not need to choose between the unlikely recovery of the authorial intention or the aridity of the sole presentation of one possible text. The New Stemmatics allows the production of an edited text that is not aimed to pretend to be the 'author's original' or the origin of a textual tradition, instead, editors could now produce the latest, well-informed, link of that textual tradition: a text that could potentially explain all extant texts at a given point in time, but that does not aspire to be 'authorial' or 'definitive.'
For a basic introduction to stemmatics and textual criticism, follow this link: Chapter II: A History of the Stemmatic Approach to the Criticism of Texts.